This invention relates to a network management system for managing a plurality of packet relay devices and managing virtual networks provided by virtual packet relay devices that are generated by packet relay devices.
Conventionally, a single packet relay device is operated as a single physical packet relay device in most cases. Virtual Router (VR) and Virtual Routing and Forwarding (VRF) are technologies related to the virtualization of a packet relay device that are used frequently in recent years. VR is a technology for virtually dividing a single packet relay device into a plurality of segments. VRF is a technology for virtually running a plurality of routing tables within a single packet relay device and thereby operating the single packet relay device virtually as a plurality of devices. A network administrator sets an arbitrary identifier to each of the virtual segments, or each of the virtually run routing tables, and manages a network based on the identifier.
The purpose of operating a single packet relay device virtually as a plurality of devices (virtual packet relay devices) is to operate a single physical network as a plurality of virtual networks by linking these virtual packet relay devices. There are the following two operation management styles which are distinguished from each other by how identifiers are assigned.
The first style involves assigning the same identifier to virtual packet relay devices that are linked, and exchanging identifiers between linked virtual packet relay devices so that the devices can each determine whether or not the other device is a member belonging to the same virtual network. Typical examples of this style include VLANs, VPNs constituted of MPLS+BGP, and VPNs constituted of VRF+BGP.
The second style does not involve exchanging identifiers between linked virtual packet relay devices but involves assigning arbitrary identifiers to virtual packet relay devices that are linked. Typical examples of this style include VR and VRF that do not use BGP. In this style, where BGP is unnecessary and arbitrary identifiers are set, virtual networks can easily be constructed at low cost but varied identifiers may be assigned to virtual packet relay devices that belong to the same virtual network while the same identifier is assigned to virtual packet relay devices that belong to different virtual networks.